Monitoring method for blinking lamps and their failure

Claim 1

A monitoring method for detecting the failure of blinking lamps and providing an indication of failure, comprising supplying an operating voltage directly across a pair of lamps in parallel during a lighted period, supplying said operating voltage across said lamps via a series resistor during the dark period of said lamps, taking a supervisory signal off said series resistor during the dark period and applying said monitoring signal to a threshold circuit, said threshold circuit responding to an upper threshold level of said monitoring signal to change over a switch controlling an oscillator generating blinking pulses, said oscillator generating a delta voltage comprising a DC component as well as an equifrequency rectangular voltage, whose frequency, in the case of a constant pulse duty factor is adjusted by varying the amplitude of the delta voltage, that from the supervisory signal and, consequently, from the lamp dark current, by comparison with a reference signal, there is derived a reference signal at that particular time position in which the dark period is to be interrupted, and that in the event of a failure of one lamp, the dark period is interrupted and simultaneously, the blinking frequency produced by the oscillator is at least doubled.